EVS 25 Shenzhen , China , Nov 5-9 , 2010 Research and Development of Wheel-motor Fuel Cell Electric Vehicle

The article gives an illustration about low speed wheel motor hybrid vehicle(LWP), firstly, introduces the structure of fuel cell vehicle and function of components; secondly, presents vehicle control policy, thirstily, takes an emulation about the power performance of LWP; lastly, experiment checking the simulation result, proofs the power performance of fuel cell vehicle.


Introduction
Developing fuel cell vehicle is an effective way to air pollution management.Fuel-cell vehicles working principle is to use hydrogen and oxygen to produce electricity, and the chemical reaction with electric drive vehicle, and the previous exercise on gasoline or diesel vehicles powered) compared with the energy efficiency and pollution emission, and many other advantages, is expected to power cars in the 21st century.But a fuel-cell car the biggest advantage is cleans, no pollution, which is the only waste water discharge.Therefore, they urged their government to formulate the corresponding policies.Currently, the United States, Europe and Japan's car manufacturers speed up to develop fuel-cell technology, maybe3-4 years, fuel-cell cars are expected to reach batch production stage, and put in the market.Although the new energy vehicles now seemed far away from the Chinese people, but as a strategic layout of automobile industry, the Chinese government has already developed new energy vehicles such as electric development direction in the future.

Fuel Cells Vehicle Structure and Theory
The main source of Fuel cell vehicle is battery, and Fuel cells for auxiliary power supply, fuel cell in parallel with the motive battery by DCDC dc converter, supplying motor and other components to drive vehicle.According to the classification of different motor, motor is divided into focus motor and wheel motors, the forth drive vehicle by a focus motor, the later drive by four-wheel motors.The 120V/12V voltage dc converter complements for12V battery.Traction battery can external connect 220V charger.This article is low-speed wheel motor hybrid vehicle as an example to introduce the fuel cell vehicle

Fuel Cell System
FC is a electrochemical reaction directly convert into electricity device by Fuel (hydrogen) and antioxidant (oxygen) chemical energy, the process does not involve burning, The mechanical consumption, Energy conversion reach up to 80%, the product is Electricity, heat and water vapor; and FC run steady, No vibration and noise, therefore, it is Considered the 21st century green energy.The following is fuel cell system working principle.FC technology applications of vehicles has brought the revolutionary breakthrough for automobile industry, at the same time improve its own development.In fact, people more consider FCEV, which is different from traditional car, the dynamic comes from FC, is not internal-combustion engine, could reduce fuel consume, generate less discharge of pollutants.When use hydrogen as fuel, it will realize the "zero emission car."As a result, it is more suitable for people Economic and environmental protection concept.Besides, when energy exhaust, FCEV is not likely traditional can which battery need more time to charge, just added fuel to continue work, it is convenient to car drivers.The table 1is introduced fuel cell system performance by wheel-motor fuel cell electric vehicle.The mainly development of FCEV has two kinds: Pure fuel-cell cars and battery-fuel cell hybrid vehicle.Pure fuel-cell cars adopt The stack with high power FC, make sure to provide force of start and Instantaneous speed if has no reserve battery; battery-fuel cell hybrid vehicle mainly use battery as the principle power, small power of fuel cell to be proceed device.

Drive System
Motor drive and control system is the device of Electrical and mechanical energy in electrical vehicle.In electric drive mode ， electricity which comes from Fuel cell engine and battery

Storage Battery Management System
Battery power is power source, the effect contain supplying power electricity in Electric mode, under Fuel cells mixed mode, Battery power and Fuel cells Provide power supply or recycled fuel cells extra energy together, and In regenerative braking feedback absorption braking energy.The table 3 is introduced battery parameters by wheel-motor fuel cell electric vehicle.Range of voltage (V) 45～100v Output total power(W) 0～6000 Auxiliary power consumption (W) 0～1000 Net output power 0～5000 system efficiency (%) >80％

Charger System
Electric vehicle with battery charger adopts high frequency switching power supply mode.Input voltage dc, rectify to ac, then High-frequency bridge switch circuit rectify to the requirements by-lowing battery.

Hydrogen Management System
Hydrogen management system using the XC164 chip CAN controller ，By receiving VMS orders to control the hydrogen electromagnetic valve on-off.At the same time detect hydrogen pressure, temperature, leak signal and sent to VMS via the can bus.Control hydrogen magnetic valve, by collecting hydrogen pressure, temperature, hydrogen leak, etc, to realize the hydrogen fuel cell system management.The table 7 is introduced hydrogen management system by wheel-motor fuel cell electric vehicle.

Display
Instruments used to display the running state of power system, which is the main way for drivers to understand condition of vehicle。 Display instrument including instrument which behind the steering wheel and the central passageway display DVD on the big screen.By CAN and signal wire, display instrument show the key components parameters and status of power system.

Feedback Braking Control Strategy
Feedback braking operation is controlled by accelerating pedal controlling motor torque to implement.Through The motor power feedback function vehicle Kinetic energy convert into electrical energy stored to the energy components in the decelerate process, In order to realize the energy recovery, achieve to save energy.
In the equation: A E is the actual feedback energy; T E is the theoretical feedback energy; is the energy consumed because of resistance.To be EV and HEV of Relations between Electric braking torque and mechanical friction slices braking torque All Parallel hybrid electric vehicle have a simple structure and control strategy.In a typical urban condition, for most of the braking energy recovery is efficient.Only in the front wheel has brake recovery.The front braking torque size has relation with Friction force generated by braking force of electric braking system and Mechanical braking system [3].

Load Balancing Strategy
Mixed electricity fuel-cell cars has a variety of power supply device, the car transient load how to reasonable Allocate to the different energy device, is usually said load equilibrium strategies.Practical load balancing suggested that is based on thinking over the influence of Power train parts characteristics, fuel economy [5]. (2) Because DC/DC converter adopt constant flow control, Power battery instantaneous power completely depend on the difference between the need of DC power by motor controller and DC/DC converter output power.The motor controller basic outputs trend is changed by the manipulation of driver instruction, as a result, load equilibrium strategies in power train system realize by Adjust DC/DC converter output power.

Fault Treatment Control System
Like traditional vehicles diagnosis and processing, the main objectives of fuel cell vehicle fault diagnosis and processing are: To ensure traffic safety, reliability and stability.In order to achieve the goal, fault processing base on classification principle is used in fuel cell vehicle.Overall processing strategies are as Table 8.

Highest Speed
Simulation curve

Purposes
The Drivers trample accelerator pedal quickly, hurry speed to 30km/h above 3. Slow fall speed 4. Stop 5. Through the drum tester, record the recorder 0 ~ 30km/h acceleration time 6.Repeat the above steps twice, take average 3 times as the final result

Conclusions
Experimental results demonstrate the wheel motor speed hybrid dynamic performance is Accord with the requirement of the theoretical simulation. Reference

Figure 1 :
Figure 1: Fuel cells vehicle structure diagram

Figure 5 :
Figure 5: Fuel-cell car DVD showed interface

Figure 6 :
Figure 6: driving force and resistance curveThe point of intersection is maximum speed:

Table 3
According to batteries, the main control VMS work is sending enables and relay closure.When BMS receiving can signal from VMS, BMS start doing relay closure.First Process is closed in battery charging relay gets charging process 100 European resistances protection in bus bar on the string.When the capacitance battery voltage is 90% percent for total voltage, main relay closure of, charge relay gets off.Relay closure action is finished BMS has a switch for charger.BMS judge For battery voltage, total voltage and temperature.

Table 7
The article Using regulate the DCDC output current to control Power battery SOC Always keep in a certain range, to maintain the demand of vehicles normal operation [4].

Table 8 :
Fault description and processing

Table 9 :
Climbing tests result